This invention relates to an article of furniture such as a desk, table or other structure having a worksurface, and more particularly to a system for providing rapid adjustment of the height of the worksurface relative to a supporting surface such as a floor.
It is known to provide a table or desk with a height adjustment feature for enabling the height of the worksurface to be adjusted relative to a supporting surface such as a floor. In a typical construction, an adjustable height table or desk includes a base having a pair of spaced apart supports or legs, which are configured to support a top or worksurface that extends between and is supported by the legs. Each leg includes a rotatably threaded rod, the upper end of which is interconnected with the worksurface. A handle or crank is interconnected with at least one of the threaded rods, such that manual rotation of the crank or handle imparts rotation to the threaded rod. A synchronizing drive arrangement, such as a chain and sprocket arrangement, is interconnected between the rods, such that rotation of one of the rods is operable to rotate the other.
In a prior art construction of this type, the table or desk must be designed to meet certain loading criteria, which is typically established either by customer requirements or by conventional testing criteria, and the height adjustment mechanism must be designed to accommodate the maximum amount of load to be supported by the worksurface. This requires the threads of the rods and the mating stationary threaded members to have a relatively high thread count, i.e. number of threads per unit length. By using a high density thread construction of this type, a relatively small amount of force is required to turn the crank or handle in order to adjust the height of the worksurface, even when the worksurface is loaded with the maximum amount of load. In this manner, the height of the worksurface can be adjusted by a wide range of users including those who are unable to apply a large amount of force to the handle, i.e. persons who do not have a great deal of arm or upper body strength.
While the above-described height adjustment mechanism provides a satisfactory arrangement for adjusting the height of a worksurface, it entails certain disadvantages in that the rate of adjustment is relatively slow and a large number of turns are required in order to accomplish even relatively small adjustment in the height of the worksurface, due to the required high density pitch of the threads of the threaded members.
It is an object of the present invention to provide a table, desk or other article of furniture having a worksurface, and including a height adjustment mechanism that is capable of providing rapid adjustment in the height of the worksurface. Yet another object of the invention is to provide such a table, desk or other article of furniture in which the height of the worksurface can be adjusted by imparting a relatively small number of revolutions to a crank or handle associated with the table, desk or other article of furniture. Yet another object of the invention is to provide a height adjustment mechanism for an article of furniture such as a table, desk or the like, which operates and is constructed in a manner generally similar to that of known worksurface height adjustment mechanisms. A still further object of the invention is to provide such a height adjustment mechanism that includes a feature for preventing inadvertent rotation of the crank or handle at all times other than when it is desired to adjust the height of the worksurface.
In accordance with the present invention, an article of furniture such as a table, desk or the like includes a base arrangement including a pair of spaced apart supports or legs and a top or other structure defining a worksurface, which extends between and is supported by the legs, in combination with a height adjustment mechanism for selectively altering the elevation of the worksurface and a lift assist or counterbalancing arrangement for loads carried by the worksurface during movement of the worksurface by operation of the height adjustment mechanism.
The height adjustment mechanism is in the form of a pair of rotatable threaded rods, each of which is interconnected at an upper end with the worksurface and is in threaded engagement with a stationary threaded member associated with one of the legs. The rods and the stationary threaded members have mating high lead threads, which provide a relatively high ratio of axial translation to angular rotation. That is, the threads of the rods and the stationary threaded members function to provide a high degree of axial adjustment, i.e. adjustment in the height of the worksurface, in response to rotation of the rods.
The lift assist or counterbalancing mechanism is configured to apply an upward bias on the worksurface. In combination with the high lead configuration of the threads on the rods and the mating threads of the stationary threaded members, the upward bias applied by the counterbalancing or lift assist mechanism functions to urge rotation of the threaded rods. In this manner, the upward bias on the worksurface provided by the lift assist or counterbalancing mechanism functions to counteract downward forces due to the weight of the worksurface as well as any loads carried by the worksurface, such that the threaded rods can be rotated relatively easily to adjust the height of the worksurface. The lift assist or counterbalancing mechanism is designed to provide a substantially constant biasing force throughout the entire range of movement of the worksurface relative to the legs.
In one embodiment, the lift assist or counterbalancing mechanism is in the form of a cylinder assembly having an extendible and retractable member that is biased in an outward direction. A pair of cables are interconnected with the extendible and retractable member. Each cable is engaged via a pulley arrangement with the extendible upper section of one of the legs, such as by engagement of the end of the cable with a cup member interconnected with the lower end of leg upper section. The extendible and retractable member is biased toward an extended position, and the cables and the pulley arrangements function to translate the outward bias of the extendible and retractable member into an upward force applied to the upper sections of the legs. The cylinder assembly is preferably mounted to a cross-member forming a part of the base of the table or desk, which extends between and interconnects the pair of spaced apart legs.
In another embodiment, the lift assist or counterbalancing mechanism is in the form of a constant force spring arrangement, in which an extendible and retractable spring strip member is biased toward a wound, retracted position. In one version, a separate spring arrangement is provided for each of the threaded rods. A cable is interconnected between each threaded rod and one of the extendible and retractable members, such as by means of a pulley arrangement. The spring arrangements are supported by a cross-member forming a part of the base and extending between the pair of spaced apart legs.
In accordance with another aspect of invention, a retainer arrangement is interposed between the worksurface and the crank or handle member, to prevent inadvertent rotation of the threaded rod. The retainer arrangement includes a hub member that is engaged with an upper end defined by one of the threaded rods, and the crank or handle member is engageable with the hub member so as to enable a user to selectively rotate the threaded rod through the crank or handle member and the hub member. The hub member and the worksurface include mating engagement structure, which is engaged so as to prevent rotation of the hub member when the hub member is in an engaged position, and is disengaged so as to enable rotation of the hub member when the hub member is in a disengaged position. The hub member is biased toward the engaged position, and is manually movable to the disengaged position by the user against the biasing force, so as to selectively enable rotation of the threaded rod through rotation of the crank or handle member. In one form, the hub member is movable along an axis coincident with the longitudinal axis of the threaded rod, for movement between the engaged and disengaged positions. In one embodiment, the worksurface includes a recess within which the upper end of the threaded rod is located, and the hub member includes a base or flange located within the recess and an outwardly extending sleeve which is configured for engagement with the crank or handle member. The worksurface includes a cover or locking member configured to enclose the recess and to overlie the base of the hub member, and to include an opening through which the sleeve extends. The engagement structure is interposed between the base of the hub member and a facing surface defined by the locking member or cover.
The invention contemplates a table, desk or other similar article of furniture having an adjustable top or worksurface, as summarized above, as well as an adjustment mechanism for a worksurface and a method of adjusting the elevation of a worksurface, substantially in accordance with the foregoing summary.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.